I enjoy working on my own.  My barrel vise is an old pipe vise , the action wrench came from ebay.  I use thick aluminum shims in both vise and wrench.

It sounds to me like you might have got a rifle that's had the chamber hogged out.  Some got rechambered to fire 30-06 blanks.  Some got really hogged out then bubba tried filling the hogged out area with an insert.  An AF Lt Col friend of mine bought one that was done that way.